syzbot


INFO: rcu detected stall in sys_unlink

Status: upstream: reported on 2025/07/20 18:19
Reported-by: syzbot+dfe0a4ce11e613b0f2f7@syzkaller.appspotmail.com
First crash: 5d03h, last: 2d07h
Similar bugs (10)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in sys_unlink (4) 1 1 115d 115d 0/3 auto-obsoleted due to no activity on 2025/07/10 21:02
linux-5.15 INFO: rcu detected stall in sys_unlink (3) 1 1 264d 264d 0/3 auto-obsoleted due to no activity on 2025/02/11 14:08
upstream INFO: rcu detected stall in sys_unlink (2) kernel 1 2 915d 999d 0/29 auto-obsoleted due to no activity on 2023/04/22 20:06
upstream INFO: rcu detected stall in sys_unlink (3) tomoyo mm 1 C error 189 5d07h 711d 0/29 upstream: reported C repro on 2023/08/13 23:42
linux-6.1 INFO: rcu detected stall in sys_unlink (2) 1 3 79d 120d 0/3 upstream: reported on 2025/03/27 11:38
linux-6.1 INFO: rcu detected stall in sys_unlink 1 4 330d 549d 0/3 auto-obsoleted due to no activity on 2024/12/07 03:28
linux-5.15 INFO: rcu detected stall in sys_unlink (2) 1 3 383d 394d 0/3 auto-obsoleted due to no activity on 2024/10/15 13:02
upstream INFO: rcu detected stall in sys_unlink kasan mm 1 1 1090d 1090d 0/29 auto-obsoleted due to no activity on 2022/10/29 07:23
linux-5.15 INFO: rcu detected stall in sys_unlink 1 1 500d 500d 0/3 auto-obsoleted due to no activity on 2024/06/20 14:47
android-5-15 BUG: soft lockup in sys_unlink 1 7 442d 464d 0/2 auto-obsoleted due to no activity on 2024/08/07 01:29

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5156/1:b..l
rcu: 	(detected by 1, t=10503 jiffies, g=55017, q=115 ncpus=2)
task:udevd           state:R  running task     stack:23144 pid:5156  ppid:1      flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14e2/0x4580 kernel/sched/core.c:6700
 preempt_schedule_irq+0xb5/0x140 kernel/sched/core.c:7010
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:legitimize_links+0x65/0x430 fs/namei.c:732
Code: de 81 e6 00 00 20 00 31 ff e8 57 7d 95 ff 81 e3 00 00 20 00 0f 85 21 03 00 00 4d 8d 6f 54 4c 89 e8 48 c1 e8 03 48 89 44 24 10 <48> b9 00 00 00 00 00 fc ff df 0f b6 04 08 84 c0 0f 85 50 03 00 00
RSP: 0018:ffffc90003247af8 EFLAGS: 00000a07
RAX: 1ffff92000648f96 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff88807d610000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90003247c68 R08: ffff888141670aa0 R09: ffff88801fd54d38
R10: ffff888141670aa0 R11: ffff88801fd54d38 R12: 1ffff92000648f8d
R13: ffffc90003247cb4 R14: dffffc0000000000 R15: ffffc90003247c60
 try_to_unlazy+0x7b/0x5a0 fs/namei.c:780
 complete_walk+0x113/0x350 fs/namei.c:891
 path_parentat fs/namei.c:2532 [inline]
 __filename_parentat+0x225/0x610 fs/namei.c:2554
 filename_parentat fs/namei.c:2572 [inline]
 do_unlinkat+0xe9/0x570 fs/namei.c:4364
 __do_sys_unlink fs/namei.c:4439 [inline]
 __se_sys_unlink fs/namei.c:4437 [inline]
 __x64_sys_unlink+0x49/0x50 fs/namei.c:4437
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f8be2315937
RSP: 002b:00007ffc08b3a828 EFLAGS: 00000202 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000000bb8 RCX: 00007f8be2315937
RDX: 0000000000000000 RSI: 00007ffc08b3a910 RDI: 0000563cce3a402e
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000001
R13: 0000563cce3bf100 R14: 0000563cce3a4008 R15: 0000000000000000
 </TASK>
rcu: rcu_preempt kthread starved for 10531 jiffies! g55017 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:27024 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14e2/0x4580 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 10844 Comm: syz.0.1162 Not tainted 6.6.99-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:____kasan_slab_free+0xfa/0x1e0 mm/kasan/common.c:229
Code: 89 c6 4c 89 f7 e8 76 45 ff ff 48 39 d8 75 75 41 f6 46 0a 08 0f 85 42 ff ff ff 48 89 df e8 1e 18 00 00 84 c0 74 43 41 8b 76 1c <ff> ce 83 ce 07 ff c6 41 0f b6 cc 48 89 df ba fb 00 00 00 e8 de 2b
RSP: 0018:ffffc9000b9dfb28 EFLAGS: 00000002
RAX: 0000000000000001 RBX: ffff888042823150 RCX: ffffea00010a08c0
RDX: 0000000000000000 RSI: 0000000000000050 RDI: 1ffff1100850462a
RBP: 0000000000000001 R08: 0000000000000070 R09: 1ffffffff2e1bc99
R10: dffffc0000000000 R11: fffffbfff2e1bc9a R12: 0000000000000000
R13: ffffc9000b9dfbb8 R14: ffff8881412673c0 R15: ffffffff81dc0c18
FS:  00007f943aa0c6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f9439db6248 CR3: 0000000062361000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1806 [inline]
 slab_free_freelist_hook+0x130/0x1b0 mm/slub.c:1832
 slab_free mm/slub.c:3816 [inline]
 kmem_cache_free+0xf8/0x280 mm/slub.c:3838
 __sigqueue_free kernel/signal.c:461 [inline]
 collect_signal kernel/signal.c:604 [inline]
 __dequeue_signal+0x52b/0x680 kernel/signal.c:626
 dequeue_signal+0xe9/0x4b0 kernel/signal.c:649
 get_signal+0x551/0x1400 kernel/signal.c:2782
 arch_do_signal_or_restart+0x96/0x780 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f9439b8e9a9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f943aa0c0e8 EFLAGS: 00000246
RAX: fffffffffffffffc RBX: 00007f9439db6248 RCX: 00007f9439b8e9a9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f9439db6248
RBP: 00007f9439db6240 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f9439db624c
R13: 0000000000000001 R14: 00007ffe3dc95b30 R15: 00007ffe3dc95c18
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/23 13:51 linux-6.6.y d96eb99e2f0e e1dd4f22 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_unlink
2025/07/20 18:18 linux-6.6.y d96eb99e2f0e 7117feec .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_unlink
* Struck through repros no longer work on HEAD.